Base station transmission power control system, mobile station and base station

ABSTRACT

In soft hand over in a code division multi access mobile radio communication system, interference in a down link caused by transmission from a plurality of base stations for one mobile station, can be restricted. Control of transmission power is performed according to command from the mobile station only in the base station serving as a primary base station which has minimum propagation loss with the mobile station during soft hand over, and the base stations other than the primary base station perform transmission with restricting output. In comparison with the transmission power control performed by the conventional plural base station transmission, interference for the peripheral mobile station can be reduced to achieve higher down link capacity. Also, upon restricting transmission power of the base station other than the base stations having small propagation loss with the mobile station among base station group in soft hand over, by moderately attenuating the transmission power instead of restricting abruptly, degradation of the reception quality can be prevented when error is caused in selection of the base station.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 10/213,166 filed on Aug. 6, 2002 now U.S. Pat. No.7,035,641, which is a continuation application of U.S. patentapplication Ser. No. 09/249,704 filed Feb. 12, 1999, now U.S. Pat. No.6,539,226 granted Mar. 25, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a mobile communicationsystem, and a mobile station and a base station to be employed therein.More particularly, the invention relates to a transmission power controlsystem in a code divided multi access (CDMA) cellular system, to whichsoft hand over is applied.

2. Description of the Related Art

In a code divided multi access (CDMA) cellular mobile telephone system,a base station transmission power control technology for controlling atransmission power of a signal to be transmitted from a base stationequipment on the basis of a power control information from a mobilestation equipment, is employed. FIGS. 30 and 31 are illustrationsrespectively showing control blocks of a mobile station and a basestation for explaining the conventionally typical base stationtransmission power control method in the CDMA cellular mobile telephonesystem.

At first, discussion will be given for a control for transmitting thepower control information from the mobile station equipment withreference to FIG. 30. In the mobile station, a transmission signal to betransmitted from the base station is received and demodulated by atransmission/reception common unit 1, an RF portion 2 and a demodulation3, and a reception quality Rq [dB] is measured by a reception qualitymeasuring device 4. Here, the reception quality is measured as a ratioof a received power of the base station transmission signal and unwantedsignal power, such as interference and so forth, or a ratio of areceived power of the base station transmission signal and an arbitraryreference received power constant.

The received reception quality Rq is compared with a required qualityRth by a comparing portion 14. When the reception quality Rq is greaterthan the required quality Rth, a transmission power control bit is setat “0” in a processing portion 15. Otherwise, the transmission powercontrol bit is set at “1” by a processing portion 16. The settransmission power control bit is inserted in a transmission signal by atransmission power control bit inserting portion 17. Also, an overheadsymbol containing various control information and so forth is insertedin an overhead inserting portion 10.

A transmission data containing the transmission power control bit and anoverhead information is transmitted to the base station via a spreadingportion 9, a modulator 8 and an amplifier device 7 of the mobile stationequipment.

Next, discussion will be given for a transmission power control in thebase station on the basis of the power control information from themobile station with reference to FIG. 31. A reception signal includingvarious data or various control information from the mobile station isreceived and demodulated via a transmission/reception common unit 21, anRF portion 22, a down converter 23, a despreading portion 24 and areception data demodulator 25. Then, the transmission power control bitis extracted in the transmission power control bit detector 31.

The extracted transmission power control bit is judged whether the valuethereof is “1” or not in a processing portion 32. If the transmissionpower control bit is “1”, a fixed transmission power control amount ΔPis added for a current transmission power control signal Pctl in aprocessing portion 33. Otherwise, the fixed transmission power controlamount Δ P is subtracted. A transmission spreading RF signal 28 isamplified by a variable amplifier 29 taking the current transmissionpower control signal Pctl as a control value and transmitted to themobile station via the transmission/reception common unit 21.

As set forth above, by the transmission power control according to thetransmission power control block diagram, the base station transmissionpower control, in which the reception quality in the mobile stationbecomes Rth, can be achieved.

In addition to the foregoing transmission power control system(hereinafter referred to as “system A”), some transmission power controlsystems have been invented. For example, in a transmission power controlsystem (hereinafter referred to as “system B”) recited in Kikuchi,Higashi, Ono, Technical Report of the Institute of Electronics,information and Communication Engineers, RCS96-13, May, 1996, pp 34,right column, links 1–15, there has been proposed a method, in which allof the base station collects communication quality information of all ofthe connected mobile stations to determine a transmission powerunitarily so as to achieve a required quality. By this method,developing of the transmission power can be completed at high speed torestrict occurrence of excessive transmission power during a periodrequired for developing the transmission power.

On the other hand, in the transmission power control system (hereinafterreferred to as “system C”) recited in Hamabe, Yoshida, Ushirokawa,Technical Report of the Institute of Electronics, Information andCommunication Engineers, RCS-84, August, 1996, pp 126, Section 2.1,there has been proposed a method, in which distribution amounts of thetransmission power of the base station for respective mobile stationsare determined by the mobile stations on the basis of a pilot receptionpower, and the base station unitarily determines the transmission powerfor respective mobile stations on the basis of the distributioninformation. Instead of seeking for the transmission power controlsystem achieving the reception quality at the desired quality inrespective mobile stations as in the systems A and B, this system C isdirected only to make the reception quality of all of the mobilestations uniform. Accordingly, while interference restriction effect isconsidered to be lower in comparison with the system A, high precisionand stable control can be performed as system makes reference to thepilot signal transmitted with high power.

In the cellular mobile communication, hand over, in which connected basestations are switched, is effected according to movement of the mobilestation. The mobile station in the CDMA cellular mobile communicationsystem, in which all base stations use the same frequencysimultaneously, interference for other radio link has to be minimized byconstantly connecting to the base station, at which a propagation lossbecomes minimum (primary base station), and by performing transmissionpower control. However, since certain period is required for hand overto new base station, delay in connection with the primary base stationcan be caused to encounter a drawback in that communication withexcessive power is inherent. Therefore, a method that the mobile stationis connected to a plurality of base stations to preliminarily take theprimary base stations, is employed. This method is referred to as softhand over (or soft hand off).

Concerning the base station transmission power control during soft handover, control system disclosed in Japanese Unexamined Patent PublicationNo. Heisei 9-74378 (hereinafter referred to as “system D”).

In the system D, concerning distribution method of the transmissionpower per the base station, there has been disclosed three methods, i.e.a method effecting distribution for equalizing the reception powers fromrespective base stations in the mobile station, a method effectingdistribution for making a ratios of the reception power from respectivebase stations in the mobile station to be equal to the pilot receptionlevel ratio, and a method effecting distribution for making thetransmission powers of respective base stations equal to the ratio ofthe pilot reception level in the mobile station.

On the other hand, a related art relating to the base stationtransmission power control during soft hand over has been disclosed incommonly owned U.S. patent application Ser. No. 09/090,013. With thedisclosed technology, reception qualities of down signals from aplurality of base stations during hand over are monitored in the mobilestation and a signal designating the base station to effect transmissionaccording to the result of monitoring is transmitted. Then, in the basestation, transmission power control of the down transmission signal tothe mobile station is performed according to the base stationdesignation signal.

The conventional transmission power control system for a down link asrepresented by the foregoing systems A to D, is premised a plural basestation transmission, in which a plurality of base stations performtransmission simultaneously during soft hand over. The soft hand over isan essential technology for realizing communication with the basestation of the minimum propagation loss in an actual system, in whichhand over control delay cannot be ignored. However, concerning the downlink, since a plurality of the base stations has to effect transmissionfor one mobile station, interference to be caused on the mobile stationcan be increased. Such problem will be discussed with reference to FIGS.32 and 33.

FIG. 32 is an illustration showing reception signals received byrespective mobile stations MS-A and MS-B located in zones Z-A and Z-Brespectively covered by the base stations BS-A and BS-B in non-soft handover state. In the shown condition, the mobile station MS-A is receivinga desired wave of a reception power of PTd-A from the connected basestation BS-A and an interference wave of reception power of PTi-B from anon-connected base station BS-B. On the other hand, the mobile stationMS-B is receiving a desired wave of a reception power of PTd-B from theconnected base station BS-B and an interference wave of reception powerof PTi-A from a non-connected base station BS-A. A ratio of the desiredwave reception power versus the interference wave reception powerobserved by the mobile station MS-B becomes PTd-B/PTi-A. Next, similarlyto FIG. 32, consideration is given for the base where soft hand over ofthe mobile station MS-A and the base station BS-B.

FIG. 33 shows the reception signals received by both mobile stationsduring soft hand over in the mobile station MS-A. The mobile stationMS-A in soft hand over receives the desired signal of the receptionpower of PTd-A from the base station BS-A and the desired signal of thereception power of PTd-A′ from the base station BS-B, namely two desiredsignals in total. By diversity reception of both desired signal waves inthe mobile station MS-A, a diversity gain can be obtained. On the otherhand, the signal transmitted by the base station BS-B for soft hand overwith the mobile station MS-A, is received as the interference wave inthe mobile station MS-B. Assuming that the reception power of theinterference wave in the mobile station MS-B is PTi-A′, the ratio of thedesired wave reception power versus the interference wave receptionpower as observed by the mobile station MS-B becomesPTd-B/(PTi-A+PTi-A′). This is smaller than PTd-B/PTi-A of the ratio ofthe desired wave reception power versus the interference wave receptionpower during non-sift hand over state set forth above to cause loweringof reception quality by increasing of interference.

Lowering of the reception quality can be compensated in certain extentby also effecting soft hand over in the mobile station MS-B. However,according to M. Soleimanpor and G. H. Freeman, Proceeding of IEEEVehicular Technology Conference, pp. 1129, right-side column, links 15to 31, in which increasing amount of interference and the diversity gainby site diversity, increasing amount of interference is greater, As aresult, capacity of the down link is restricted. Similar assertion hasalso be seen in Nakano, Umeda, Ohno, Technical Report of the Instituteof Electronics, Information and Communication Engineers, RCS94-100, pp71, left column, links 1 to 8.

It should be noted that increasing of interference by the plural basestation transmission of the down link set forth above will not raiseproblem in so-called hard hand over in which simultaneous communicationbetween a plurality of base stations and the mobile station is notperformed. In this case, influence of hand over period of the basestation namely hand over control delay can be a problem. According toFurukawa, Communication Society Conference 1997 of the Institute ofElectronics, Information and Communication Engineers, pp. 264, Chapter3, it is stated that greater transmission power is radiated at greaterhand over control delay. Hard hand over under a condition where the handover control delay cannot be ignored, is inherently performed at anexcessive transmission power for the mobile station in formerlyconnected base station before hand over in order to forcedly establishcommunication with the formerly connected base station which iscurrently non-minimum propagation loss base station for the mobilestation. As a result, interference for the peripheral mobile stations isincreased.

In order to reflect the transmission power control signal from themobile station in the base station with high fidelity, the transmissionpower control signal has to be transmitted with small error and smalldelay. On the other hand, in order to effectively use the communicationlink, it is desirable that a power of the transmission power controlsignal is as small as possible. As a technology for reducing receptionerror, there is a method of interleave, error correction and so forthapplied for transmission of the signal of voice, data and so forth.However, this technology is not applied to the transmission powercontrol signal for causing increasing of decoding delay or additionalinformation. As a result, frequency of occurrence of error of thetransmission power control signal becomes high in comparison with thedata signal. Particularly, upon soft hand over, in the non-primary basestation, in which propagation loss is large, reception error becomeslarge.

When reception error of the transmission power control signal is caused,the transmission power control command from the mobile station cannot bereflected well. Thus, the base station is forced to performcommunication at inappropriate transmission power. This will bediscussed with reference to FIG. 34. FIG. 34 illustrates variation ofthe transmission power in time PT-A, PT-B and PT-A′, PT-B′ of respectivebase station while soft hand over is performed between a certain mobilestation and two base stations BS-A and BS-B. In FIG. 34, a vertical axisrepresents a transmission power [dBW] of base station and a horizontalaxis represents a time [sec].

As shown in FIG. 34, when reception error is not caused in thetransmission power control, as illustrated by solid links of variationin time transitions PT-A and PT-B, the transmission power of both basestations are maintained at equal value. On the other hand, whenreception error is caused in the transmission power control signal asillustrated by dotted link of variation in time transitions PT-A andPT-B, it can be appreciated that lacking of the transmission power iscontinuously caused in PT-A and excessive transmission power iscontinuously caused in PT-B. Particularly, when excessive transmissionpower is continuously caused as in the variation in time transitionPT-B, interference is caused for the peripheral cells to reduce capacityto be received in the system.

SUMMARY OF THE INVENTION

It is an object of the present invention to obtain high down linkcapacity with restricting increasing of interference by plural basestation transmission upon soft hand over.

Another object of the present invention is to prevent excessiveradiation of a transmission power due to switching of connection of basestations upon hand over, namely due to hand over control delay.

A further object of the present invention is to prevent base stationgroup from transmitting inappropriate transmission power due toreception error of a transmission power control signal during soft handover.

A still further object of the present invention is to prevent increasingof interference by a plurality of base stations during soft hand over ofdown link.

According to the first aspect of the present invention, a base stationtransmission power control system in a code division multi accesscellular mobile radio communication system comprises a plurality of basestations respectively announcing unique pilot signals and a mobilestation which is capable of simultaneously establishing connection witha soft hand over base station group consisted of some of base stationsout of the base stations in the system, wherein the soft hand over basestation group includes a primary base station having minimum propagationloss with the mobile station during soft hand over and remaining basestations being restricted outputs.

According to the second aspect of the present invention, a base stationtransmission power control system in a code division multi accesscellular mobile radio communication system comprises a plurality of basestations respectively announcing unique pilot signals and a mobilestation which is capable of simultaneously establishing connection witha soft hand over base station group consisted of some of base stationsout of the base stations in the system, wherein

the mobile station detects a communication reception quality and aprimary base station among the base stations, reception level of pilotsignal of which becomes maximum among pilot signals received fromrespective base stations in the soft hand over base station group,notifies a base station number of the primary base station as atransmission power control signal for respective of the base stations inthe soft hand over base station group when the communication receptionquality is lower than a desired quality, and notifies a number otherthan the base station number of the base stations in the soft hand overbase station group when the communication reception quality is in excessof the desired quality; and

each base station in the soft hand over base station group receives thetransmission power control signal and being restricted a transmissionpower when a content of the transmission power control signal identifiesnumber other than own base station number.

According to the third aspect of the present invention, a base stationtransmission power control system in a code division multi accesscellular mobile radio communication system comprises a plurality of basestations respectively announcing unique pilot signals and a mobilestation which is capable of simultaneously establishing connection witha soft hand over base station group consisted of some of base stationsout of the base stations in the system, wherein

the mobile station detects a communication reception quality and aprimary base station among the base stations, reception level of pilotsignal of which becomes maximum among pilot signals received fromrespective base stations in the soft hand over base station group,increases and decreases the base station transmission power valuemanaged by the mobile station so that the communication receptionquality becomes a desired quality, and transmits a transmission powercontrol signal consisted of a base station number of the primary basestation and the base station transmission power value to the soft handover base station group, and

each base station of the soft hand over base station group receives thetransmission power control signal, setting the base station transmissionpower value managed by the mobile station and contained in thetransmission power control signal to a transmission power value of ownstation when the base station number contained in the transmission powercontrol signal is consistent with own base station number, and sets thetransmission power value of own station at a restricted transmissionpower value when the base station number contained in the transmissionpower control signal is not consistent with own base station number.

According to the fourth aspect of the present invention, a base stationtransmission power control system in a code division multi accesscellular mobile radio communication system comprises a plurality of basestations respectively announcing unique pilot signals and a mobilestation which is capable of simultaneously establishing connection witha soft hand over base station group consisted of some of base stationsout of the base stations in the system, wherein

the mobile station detects a communication reception quality and aprimary base station among the base stations, reception level of pilotsignal of which becomes maximum among pilot signals received fromrespective base stations in the soft hand over base station group, setsa power increasing symbol in a transmission power control bit when thecommunication reception quality does not exceed the desired quality,setting a power decreasing symbol in the transmission power control bitwhen the communication reception quality exceeds the desired quality,and transmits the transmission power control bit to the soft hand overbase station group and intermittently transmitting the primary basestation number, and

each base station of the soft hand over base station group receiving thetransmission power control signal which includes a primary base stationnumber, and restricting a transmission power of one station following tothe current timing when the primary base station number is notconsistent with own base station number.

15. A base station transmission power control system in a code divisionmulti access cellular mobile radio communication system comprising aplurality of base stations respectively announcing unique pilot signalsand a mobile station which is capable of simultaneously establishingconnection with a soft hand over base station group consisted of some ofbase stations out of the base stations in the system, wherein

the mobile station detecting a communication reception quality and aprimary base station among the base stations, reception level of pilotsignal of which becomes maximum among pilot signals received fromrespective base stations in the soft hand over base station group,setting a power increasing symbol in a transmission power control bitwhen the communication reception quality does not exceed the desiredquality, setting a power decreasing symbol in the transmission powercontrol bit when the communication reception quality exceeds the desiredquality, transmits a transmission power control signal consisted of thetransmission power control bit or a transmission power control signalconsisted of the primary base station number to the soft hand over basestation, and

each base station in the soft hand over base station group receives thetransmission power control signal, and restricts a transmission power ofown station for current and subsequent timing when the primary basestation number is not consistent with own base station number.

According to the fifth aspect of the present invention, a mobile stationin a code division multi access cellular mobile radio communicationsystem comprising a plurality of base stations respectively announcingunique pilot signals and capable of simultaneously establishingconnection with a soft hand over base station group consisted of some ofbase stations out of the base stations in the system, comprises:

primary base station determining means for determining a primary basestation having a minimum propagation loss during soft hand over; and

commanding means for commanding restriction of a transmission power forthe base stations in the soft hand over base station group other thanthe primary base station.

According to the sixth aspect of the present invention, a mobile stationin a code division multi access cellular mobile radio communicationsystem comprising a plurality of base stations respectively announcingunique pilot signals and capable of simultaneously establishingconnection with a soft hand over base station group consisted of some ofbase stations out of the base stations in the system, comprises:

means for detecting a primary base station which transmits a pilotsignal of the maximum reception level at the mobile station amongreceived pilot signals from the base stations in the soft hand over basestation group, and

means for transmitting a transmission power control signal consisted ofthe base station number of the primary base station and the base stationtransmission power value by increasing and decreasing the base stationtransmission power value managed by the mobile station so that thereception quality becomes a desired quality.

According to the seventh aspect of the present invention, a base stationin a code division multi access cellular mobile radio communicationsystem announcing a unique pilot signal and is capable of simultaneouslyestablishing connection with a mobile station together with other basestations in a soft hand over base station group consisted of some ofbase stations, comprises:

transmission power control signal detecting means for detecting atransmission power control signal from the mobile station; and

transmission power control means for restricting a transmission powerwhen a primary base station information in the transmission powercontrol signal does not identify own station.

According to the eighth aspect of the present invention, a mobilestation in a code division multi access cellular mobile radiocommunication system comprising a plurality of base stationsrespectively announcing unique pilot signals and capable ofsimultaneously establishing connection with a soft hand over basestation group consisted of some of base stations out of the basestations in the system, comprises:

reception quality detecting means for detecting a communicationreception quality; primary base station detecting means for detectingprimary base station which transmits a pilot signal of the maximumreception level at the mobile station among received pilot signals fromthe base stations in the soft hand over base station group;

base station transmission power managing means for holding a basestation transmission power value, increasing the base stationtransmission power value when the communication reception qualitydetected by the reception quality detecting means does not exceed adesired quality and decreasing the base station transmission power valuewhen the communication reception quality detected by the receptionquality detecting means exceeds the desired quality; and

control signal transmitting means for transmitting the primary basestation information detected by the primary base station detecting meansand the base station transmission power value held in the base stationtransmission power managing means as a transmission power control signalto the soft hand over base station group.

According to the ninth aspect of the present invention, a base stationin a code division multi access cellular mobile ratio communicationsystem announcing a unique pilot signal and is capable of simultaneouslyestablishing connection with a mobile station together with other basestations in a soft hand over base station group consisted of some ofbase stations, comprises:

control signal receiving means for receiving a transmission powercontrol signal from the mobile station;

control signal separating means for separating a primary base stationinformation and a base station transmission power value information fromthe transmission power control signal; and

transmission power control means for performing transmission with thebase station transmission power indicated by the base stationtransmission power value information when the primary base stationinformation separated by the control signal separating means indicates abase station information of own station, and performing transmissionwith a minimum transmission power when the primary base stationinformation detected by the control signal separating means does notindicate the base station information of own station.

According to the tenth aspect of the present invention, a mobile stationin a code division multi access cellular mobile radio communicationsystem comprising a plurality of base stations respectively announcingunique pilot signals and capable of simultaneously establishingconnection with a soft hand over base station group consisted of some ofbase stations out of the base stations in the system, comprising:

reception quality detecting means for detecting a communicationreception quality; primary base station detecting means for detectingprimary base station which transmits a pilot signal of the maximumreception level at the mobile station among received pilot signals fromthe base stations in the soft hand over base station group;

base station transmission power control signal determining means forsetting a base station transmission power control signal for increasingpower when the communication reception quality detected by the receptionquality detecting means does not exceed a desired quality and settingthe base station transmission power control signal for decreasing powerwhen the communication reception quality detected by the receptionquality detecting means exceeds a desired quality; and

control signal transmitting means for transmitting the base stationtransmission power control signal determined by the base station controlsignal determining means to the base station group in soft hand over orintermittently transmitting a primary base station information detectedby the primary base station detecting means and the base stationtransmission power control signal determined by the base station controlsignal determining means to the base station group in soft hand over.

According to the eleventh aspect of the present invention, a basestation in a code division multi access cellular mobile radiocommunication system announcing a unique pilot signal and is capable ofsimultaneously establishing connection with a mobile station togetherwith other base stations in a soft hand over base station groupconsisted of some of base stations, comprises:

control signal receiving means for receiving a transmission powercontrol signal from the mobile station;

primary base station information separating means for separating aprimary base station information and a base station transmission powervalue information from the transmission power control signal; and

transmission power control means for increasing and decreasing atransmission power for current and subsequent timing according to thetransmission power control signal when the primary base stationinformation is contained in the transmission power control signal andthe primary base station information indicates the base stationinformation of own station and setting the transmission power to aminimum transmission power for current and subsequent timing when theprimary base station information is contained in the transmission powercontrol signal and the primary base station information does notindicate the base station information of own station.

According to the twelfth aspect of the present invention, a mobilestation in a code division multi access cellular mobile radiocommunication system comprising a plurality of base stationsrespectively announcing unique pilot signals and capable ofsimultaneously establishing connection with a soft hand over basestation group consisted of some of base stations out of the basestations in the system, comprises:

reception quality detecting means for detecting a communicationreception quality; primary base station detecting means for detectingprimary base station which transmits a pilot signal of the maximumreception level at the mobile station among received pilot signals fromthe base stations in the soft hand over base station group;

base station transmission power control signal determining means forsetting a base station transmission power control signal for increasingpower when the communication reception quality detected by the receptionquality detecting means does not exceed a desired quality and settingthe base station transmission power control signal for decreasing powerwhen the communication reception quality detected by the receptionquality detecting means exceeds a desired quality; and

control signal transmitting means for transmitting the base stationtransmission power control signal determined by the base station controlsignal determining means to the base station group in soft hand over orregularly transmitting a primary base station information detected bythe primary base station detecting means as the transmission powercontrol signal to the base station group in soft hand over.

According to the thirteenth aspect of the present invention, a basestation in a code division multi access cellular mobile ratiocommunication system announcing a unique pilot signal and is capable ofsimultaneously establishing connection with a mobile station togetherwith other base stations in a soft hand over base station groupconsisted of some of base stations, comprising:

control signal receiving means for receiving a transmission powercontrol signal from the mobile station; and

transmission power control means for increasing and decreasing atransmission power for current and subsequent timing according to thetransmission power control signal when a primary base stationinformation is contained in the transmission power control signal andthe primary base station information indicates the base stationinformation of own station and setting the transmission power to aminimum transmission power for current and subsequent timing when theprimary base station information is contained in the transmission powercontrol signal and the primary base station information does notindicate the base station information of own station.

According to the fourteenth aspect of the present invention, a mobilecommunication system comprises:

a mobile station; and

a plurality of base stations adapted for communication with the mobilestation, one or more base stations having propagation loss incommunication with the mobile station smaller than a predeterminedthreshold value during soft hand over being selected as communicationstations, transmission power of a base station group of the basestations other than those selected as the communication stations beingcontrolled for sequentially attenuating toward a predetermined minimumpower with a given attenuation amount.

According to the fifteenth aspect of the present invention, a cellularmobile communication system including, a plurality of base stations andmobile station, comprises:

base station number assigning means for temporarily assigning basestation numbers for a plurality of base stations in soft hand over withthe mobile station;

base station selecting means for selecting the base station whichtransmits a pilot signal received by the mobile station at a maximumreception intensity among pilot signals transmitted from the basestation in soft hand over;

transmission power control signal transmitting means for using a basestation number of the selected base station as a transmission powercontrol signal to be transmitted to the base station group in soft handover from the mobile station; and

transmission power control means for controlling the transmission powerof the base station on the basis of the transmission power controlsignal,

the transmission power of the base station other than the selected basestation being controlled for sequentially attenuating toward apredetermined minimum power with a given attenuation amount.

According to the sixteenth aspect of the present invention, acommunication control method in a cellular mobile communication systemincluding a plurality of base stations and mobile station, comprises:

base station number assigning step of temporarily assigning base stationnumbers for a plurality of base stations in soft hand over with themobile station;

base station selecting step of selecting the base station whichtransmits a pilot signal received by the mobile station at a maximumreception intensity among pilot signals transmitted from the basestation in soft hand over;

transmission power control signal transmitting step of using a basestation number of the selected base station as a transmission powercontrol signal to be transmitted to the base station group in soft handover from the mobile station; and

transmission power control step of controlling the transmission power ofthe base station on the basis of the transmission power control signal,

the transmission power of the base station other than the selected basestation being controlled for sequentially attenuating toward apredetermined minimum power with a given attenuation amount.

According to the seventeenth aspect of the present invention, a mobilestation in a code division multi access cellular mobile radiocommunication system comprising a plurality of base stationsrespectively announcing unique pilot signals and capable ofsimultaneously establishing connection with a soft hand over basestation group consisted of some of base stations out of the basestations in the system, comprising:

primary base station determining means for determining a primary basestation having a minimum propagation loss during soft hand over; and

transmitting means for sequentially commanding attenuation control oftransmission power for the base stations in the soft hand over basestation group other than the primary base station, with a givenattenuation amount.

According to the eighteenth aspect of the present invention, a basestation in a cellular mobile communication system temporarily assignedthe base station number by a mobile station in soft hand over with themobile station, comprises:

means for transmitting a pilot signal;

judgment means for receiving a transmission power control signalincluding a base station number selected as base station which transmitsa pilot signal received by the mobile station at a maximum receptionintensity among pilot signals transmitted from the base station in softhand over and making judgment whether the base station number isconsistent with a number assigned to own station or not; and

transmission power control means for performing sequential attenuationcontrol of the transmission power with a given attenuation amount whenthe base station number and the number of own station are inconsistentwith each other.

With the present invention set forth above, increasing of interferencein the down link due to plural base stations transmission causingproblem in soft hand over, can be avoided by restricting transmissionpower of the base stations other than the primary base stations uponsoft hand over. On the other hand, under the premise of application ofsoft hand over, connection between the mobile station and the minimumpropagation loss base station can be assured under presence of hand overcontrol delay. Accordingly, excessive radiation of the transmissionpower of the former base stations before hand over due to hand overcontrol delay to be a problem in hand over.

Also, by moderately attenuating the transmission power instead ofabruptly restricting upon restricting the transmission power of the basestations other than the base station having small propagation loss withthe mobile station among the base station group during soft hand over,abrupt lowering of the desired signal reception intensity in the mobilestation is not caused even when error in selection of the base stationis caused. Thus, significant degradation of reception quality asobserved in the conventional system shown in FIG. 34 can be prevented.

Furthermore, by making the mobile station to selected one or severalbase stations having small propagation loss with the mobile station,namely small reception error of the transmission power control signal asbeing assigned for transmission, transmission with inappropriatetransmission power due to reception error of the transmission powercontrol signal can be successfully avoided. Furthermore, the value ofvirtual base station transmission power is indicative of a set targetvalue of the transmission output value of the base station aftercommunication with minimum transmission power without selection of ownbase station for a while. By this, upon switching of the communicationstation of the mobile station, degradation of quality and excessivequality can be prevented.

On the other hand, instead of all base stations during soft hand over, apart of the base stations are assigned for transmission to the mobilestation to successfully reduce interference of the down link. As aresult, high down link capacity can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given herebelow and from the accompanying drawings of thepreferred embodiment of the present invention, which, however, shouldnot be taken to be limitative to the invention, but are for explanationand understanding only.

In the drawings:

FIG. 1 is an illustration showing an embodiment of a mobile stationaccording to the present invention;

FIG. 2 is an illustration showing an embodiment of a base stationaccording to the present invention;

FIG. 3 is an illustration showing an operation of a transmission powercontrol information symbol generating portion in the shown embodiment ofthe mobile station;

FIG. 4 is an illustration showing an operation of a transmission powercontrol portion in the base station corresponding to the mobile stationshown in FIG. 3;

FIG. 5 is an illustration showing a cellular mobile station arrangementfor explaining soft hand over of the present invention;

FIG. 6 is an illustration showing variation of transmission power of thebase station in time according to the present invention;

FIG. 7 is an illustration showing variation of transmission power of thebase station in time in the prior art;

FIG. 8 is an illustration showing an operation of the transmission powercontrol portion of another embodiment of the base station correspondingto the mobile station shown in FIG. 4;

FIG. 9 is an illustration showing an operation of the transmission powercontrol information symbol generating portion of another embodiment ofthe mobile station according to the present invention;

FIG. 10 is an illustration showing an operation of the transmissionpower control portion of another embodiment of the base stationcorresponding to the mobile station shown in FIG. 9;

FIG. 11 is an illustration showing an operation of the transmissionpower control information symbol generating portion of anotherembodiment of the mobile station of FIG. 9;

FIG. 12 is an illustration showing an operation of the transmissionpower control information symbol generating portion of a furtherembodiment of the mobile station according to the present invention;

FIG. 13 is an illustration showing an operation of the transmissionpower control portion of a further embodiment of the base stationcorresponding to the mobile station shown in FIG. 12;

FIG. 14 is an illustration showing an operation of the transmissionpower control information symbol generating portion of a furtherembodiment of the mobile station of FIG. 12;

FIG. 15 is an illustration showing an operation of a transmission powercontrol portion of a further embodiment of the base station shown inFIG. 13;

FIG. 16 is an illustration showing an operation of the transmissionpower control information symbol generating portion of a still furtherembodiment of the mobile station of FIGS. 12 and 14;

FIG. 17 is an illustration showing an operation of the transmissionpower control portion of a still further embodiment of the base stationshown in FIG. 13 or 15;

FIG. 18 is an illustration showing an operation of the transmissionpower control portion of a still further embodiment of the base stationshown in FIG. 13, 15 or 17;

FIG. 19 is an illustration showing examples of variation of thetransmission power PT-A and PT-B in time in each base station when theprior art is applied upon soft hand over between the mobile station andtwo base stations BS-A and BS-B;

FIG. 20 is a block diagram of an embodiment of the mobile stationaccording to the present invention;

FIG. 21 is a block diagram of an embodiment of the base stationaccording to the present invention;

FIG. 22 is an illustration showing a process of the transmission powercontrol information symbol generating portion in the block diagram ofFIG. 20;

FIG. 23 is an illustration showing a process of the transmission powercontrol portion in the block diagram shown in FIG. 21;

FIG. 24 is an illustration showing one example of the process of a basestation number information portion in the block diagram of FIG. 20;

FIG. 25 is an illustration showing an example of a transmission powercontrol symbol Spct and an actual bit string indicative thereof;

FIG. 26 is an illustration showing another example of the process of thebase station number information portion in the block diagram of FIG. 20;

FIG. 27 is an illustration showing a further example of the process ofthe base station number information portion in the block diagram of FIG.20;

FIG. 28 is an illustration showing examples of variation of thetransmission power PT-A and PT-B in time in each base station when thepresent invention is applied upon soft hand over between the mobilestation and two base stations BS-A and BS-B;

FIG. 29 is a chart of format showing a transmission side of thetransmission power control information symbol;

FIG. 30 is a block diagram of the conventional mobile station;

FIG. 31 is a block diagram showing the conventional base station;

FIG. 32 is an illustration showing a signal received by the mobilestation in the case where the soft hand over is not performed;

FIG. 33 is an illustration showing a signal received by the mobilestation when the soft hand over is performed; and

FIG. 34 is an illustration showing examples of variation of thetransmission power PT-A and PT-B in time in each base station when theprior art is applied upon soft hand over between the mobile station andtwo base stations BS-A and BS-B.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be discussed hereinafter in detail in termsof the preferred embodiment of the present invention with reference tothe accompanying drawings. In the following description, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be obvious, however, tothose skilled in the art that the present invention may be practicedwithout these specific details. In other instance, well-known structuresare not shown in detail in order to avoid unnecessarily obscure thepresent invention.

One embodiment of a base station transmission power control system, amobile station and a base station according to the present inventionwill be discussed hereinafter.

FIG. 1 is an illustration showing a construction of the shown embodimentof the mobile station. The mobile station is constructed with an RFportion 2 performing a reception process of a signal received from thebase station, a demodulation circuit 3, a reception quality measuringdevice 4 detecting a reception quality of a received signal and amaximum pilot reception signal, a pilot signal reception intensitymeasuring device 5, a maximum pilot reception signal detector 18, atransmission power control information symbol generating portion 12generating a transmission power control information of the base stationto be inserted in a signal to be transmitted to the base station, atransmission information portion 11 outputting a transmission signal, atransmission power control information symbol inserting portion 17inserting the transmission power control information symbol in thetransmission signal, a spreading portion 9 inserting necessary overheadinformation, performing modulation process and transmitting, a modulator8, an amplifier device 7 and a transmission/reception common unit 1.

A transmission signal transmitted from the base station is received viathe transmission/reception common unit 1, the RF portion 2 and thedemodulation circuit 3 of the mobile station. A reception quality Rq[dB] of the transmission signal is measured by the reception qualitymeasuring device 4. On the other hand, a pilot signal radiated from eachbase station and included in the output of the RF portion 2 is receivedthe maximum pilot reception signal detector 18 via the pilot signalreception intensity measuring device 5. In the maximum pilot receptionsignal detector 18, an index Bpmi of the base station having the minimumpropagation loss and transmitting the pilot signal having the maximumreception power, is detected. Here, as the base station index, whennumber of base stations of the maximum soft hand over, mutually distinctnumbers among 1 to n are assigned for respective base stationsassociated with soft hand over.

The reception quality Rq and the minimum propagation loss base stationindex Bpmi are input to the transmission power control informationsymbol generating portion 12. In the transmission power controlinformation symbol generating portion 12, a transmission power controlinformation symbol Spct designating a transmission signal level for thebase station is generated. The transmission power control informationsymbol Spct is inserted in the transmission signal output from thetransmission information portion 11 in the transmission power controlinformation symbol inserting portion 17. Furthermore, the transmissionsignal of output of the overhead inserting portion 10 is inserted anoverhead information in the overhead inserting portion 10. Thetransmission signal containing the transmission information, thetransmission power control information and the overhead information istransmitted toward the base station via the spreading portion 9, themodulator 8, the amplifier device 7 and the transmission/receptioncommon unit 1.

FIG. 2 is an illustration showing a construction of the shown embodimentof the base station. The base station performs demodulation process orso forth of the signal received from the mobile station. The basestation is constructed with an RF portion 22, a frequency down converter23, a despreading portion 24, a reception data demodulator 25, atransmission power control symbol detector 26 extracting thetransmission power control information determining an output level ofthe RF signal transmitted from the base station from the receptionsignal, a transmission power control portion 27, a transmissionspreading RF signal portion 28 outputting the transmission signalcontaining the pilot signal to be transmitted to the mobile station, avariable output amplifier 29 controlling output level of thetransmission signal on the basis of the transmission power controlinformation and a transmission/reception common unit 21.

The transmission signal containing the transmission power controlinformation transmitted from the mobile station is input to thetransmission power control symbol detector 26 via thetransmission/reception common unit 21, the RF portion 22, the frequencydown converter 23, the despreading portion 24 and the reception datademodulator 25. The transmission power control symbol detector 26detects a transmission power control information Spcr. The transmissionpower control information Spcr is input to the transmission powercontrol portion 27. Then, the transmission power control portion 27 setsthe output level [dBW] of the variable output amplifier 29 at a controlvalue Pctl on the basis of the transmission power control informationSpcr.

The transmission signal to the mobile station output from thetransmission spreading RF signal portion 28 is amplified by the variableoutput amplifier 29 which is controlled by the signal Pctl and istransmitted toward the mobile station via the transmission/receptioncommon unit 21.

FIGS. 3 and 4 are flow diagrams showing one embodiment of signalprocessing of the transmission power control information symbolgenerating portion 12 of the mobile station and the transmission powercontrol portion 27 of the base station in the base station transmissionpower control system according to the present invention.

At first, discussion will be given for operation of the transmissionpower control information symbol generating portion 12 in the mobilestation shown in FIG. 3. The reception quality Rq measured in the mobilestation is compared with a quality threshold value Rth [dB] in controlstep PA001. As a result of comparison, if Rq>Rth, the transmission powercontrol information symbol Spct is set to 0 at control step PA002.Otherwise, Spct is set equal to Bpmi at control step PA003 to output anyone of the transmission power control information symbols Spct is outputat control step PA004.

Next, discussion will be given for operation of the transmission powercontrol portion 27 in the base station shown in FIG. 4. The transmissionpower control information Spcr detected by the transmission powercontrol symbol detector 26 is judged whether it is set to 0 at controlstep CB001. If the transmission power control information Spcr is not 0,a transmission power control amount ΔPu [dB] is added to a current basestation transmission power Pbsm [dBW] directed toward the mobile stationwhich transmits the transmission power control information Spcr, atcontrol step CB002. On the other hand, if the transmission power controlinformation Spcr is 0, a transmission power control amount (powerattenuation amount) ΔPd [dB] is subtracted from the base stationtransmission power Pbsm at control step CB003.

When ΔPu is added to the base station transmission power Pbsm is addedat the control step CB002, check is performed whether the transmissionpower control information Spcr and the index number of the own basestation are consistent with each other or not at step CB004. If thetransmission power control information Spcr and the index number of theown base station are consistent with each other, transmission flag Fstis set to 1 at control step CB005. On the other hand, if thetransmission power control information Spcr and the index number of theown base station are not consistent with each other, the transmissionflag Fst is set to 0 at control step CB006. Here, the initial value ofthe transmission flag Fst is 0, and is constantly held until beingvaried subsequently.

When ΔPu is subtracted from the current base station transmission powerPbsm at control step CB003, the value of the transmission flag Fst isheld as the preceding value.

Then, at control step CB007, the control value Pctl [dBW] of thevariable output amplifier 29 shown in FIG. 2 is derived through thefollowing formula:Pctl←Pbsm×Fst+Pmin×(1−Fst)  (1)

wherein Pmin [dBW] represents a minimum transmission power in the basestation.

The control value Pctl obtained through the foregoing formula (1) atcontrol step CB007 is output to the variable output amplifier 29. Then,the base station transmission power is controlled to the control valuePctl [dBW] by the variable output amplifier 29.

Operation of the base station transmission power control during softhand over in the shown embodiment of the base station transmission powercontrol system will be discussed with reference to FIGS. 5, 6 and 7.

As shown in FIG. 5, the mobile station MS in motion in a Cus directionis assumed that is performing soft hand over with three base stationsBS#1, BS#2 and BS#3. The mobile station MS has the construction shown inFIG. 1 and constantly transmits the transmission power controlinformation symbol Spct toward the base stations BS#1 to BS#3 in themethod shown in FIG. 3. On the other hand, each of the base stationsBS#1 to BS#3 has a construction shown in FIG. 2. The output if thevariable output amplifier 29 is controlled to the control value Pctl inthe method shown in FIG. 4. Here, the power increasing amount ΔPu andthe power attenuation amount ΔPd become equal value.

When the shown embodiment of the transmission power control method isapplied, variation of the transmission power in time of the basestations BS#1 to BS#3 toward the mobile station MS is as illustrated bysolid link in FIG. 6. P-BS#1, P-BS#2 and P-BS#3 respectively showvariation of the transmission power in time of respective base stationsBS#1, BS#2 and BS#3. In FIG. 6, the vertical axis represents the basestation transmission power [dBW] and the horizontal axis represents atime [sec].

In the shown embodiment of the transmission power control method asillustrated in the time dependent variation P-BS#2 shown by the solidlink in FIG. 6, during a period from a time T0 [sec] to a time T1 [sec],only base station BS#2 performs transmission and base stations BS#1 andBS#3 perform transmission at minimum transmission power. On the otherhand, during a period from the time T1 [sec] to T2 [sec], only basestation BS#1 performs transmission as shown by time dependent variationP-BS#1, and the base stations BS2 and BS3 perform transmission atminimum transmission power.

By the shown embodiment of the transmission power control method, theprimary base station, in which the reception level of the pilot signalreceived by the mobile station becomes constantly minimum propagationloss, is selected depending upon the reception level of the pilot signalreceived by the mobile station. Then, only primary base stationtransmits the transmission wave and other base stations are restrictedoutput of the transmission wave for suppressing increasing ofinterference. This nominally equivalent to the condition where instanthard hand over having no hand over control delay is realized.

On the other hand, FIG. 7 shows the base station transmission power inthe case where the conventional transmission power control shown inFIGS. 30 and 31 is applied. C-BS#1, C-BS#2 and C-BS#3 represent timedependent variation of the transmission power of respective basestations BS#1, BS#2 and BS#3. In the transmission power control in theconventional method, all of the three base stations transmits the equaltransmission power toward the mobile station MS as shown in FIG. 7, highinterference in comparison with the transmission power control methodaccording to the present invention, can be caused in the peripheralmobile station.

On the other hand, in the sequential base station transmission powercontrol according to designation of increasing or decreasing of thepower from the mobile station, error should be caused in increasing anddecreasing control of the base station transmission power by thereception error of the control signal.

In the transmission power control according to the present invention,even when error is caused in increasing and decreasing control of thebase station transmission power, for example, since the transmissionpower is restricted for the base stations other than the primary basestation, influence can be made small.

Next, another embodiment of the base station transmission power controlsystem, the mobile station and the base stations according to thepresent invention will be discussed.

FIG. 8 shows a construction of another embodiment of the base stationaccording to the present invention, in which a different construction ofthe transmission power control portion 27 in the base station discussedwith reference to FIG. 4 is illustrated. Namely, FIG. 8 illustratesdifferent construction of the transmission power control portion 27corresponding to the transmission power control information symbolgenerating portion 12 shown in FIG. 3.

In the shown embodiment, increasing and decreasing control of thetransmission power of a given amount is performed depending upon whetherthe transmission power control information symbol Spcr from the mobilestation is matched with the index number of own base station or not.Variation of the transmission power of the base station by switching ofthe primary base station can be made as moderate time dependentvariation as shown by dotted link in FIG. 6.

In the transmission power control symbol detector 26 of the base stationshown in FIG. 2, concerning the detected transmission power controlinformation symbol Spcr, the transmission power control informationsymbol Spcr and the index number of own base station are compared atcontrol step CA001. If the transmission power control information symbolSpcr and the index number of own base station are equal to each other,the power increasing amount ΔPu [dB] is added to the control value Pctl[dBW] of the output of the variable output amplifier 29 at control stepCA003. If the transmission power control information symbol Spcr and theindex number of own base station are not equal to each other, process tosubtract the power attenuation amount ΔPd [dB] from the control valuePctl [dBW] at step CA002, is performed. The resultant value Pctl [dBW]of addition or subtraction is output toward the variable outputamplifier 29 at step CA004. In the base station of the shown embodiment,the base station transmission power control system according to thepresent invention which enables soft hand over operation with the mobilestation having the transmission power control information symbolgenerating portion 12 shown in FIG. 3, is incorporated.

Also, as a further embodiment of the mobile station and the base stationaccording to the present invention, in which the transmission powercontrol information symbol generating portion 12 and the transmissionpower control portion 27 having constructions different from the formerembodiment, will be discussed with reference to FIGS. 9 and 10. In theshown embodiment, the mobile station manages the base stationtransmission power value to be transmitted from the primary base stationto constantly transmit the base station transmission power value and theminimum propagation loss base station index. In the transmission powercontrol information symbol generating portion 12 shown in FIG. 9,setting for reflecting a difference between the reception quality Rq andthe given quality threshold value Rth in the base station transmissionpower value is performed.

At first, discussion will be given for the transmission power controlinformation symbol generating portion 12.

FIG. 9 is an illustration showing a construction of the transmissionpower control information symbol generating portion 12 of the shownembodiment of the mobile station.

At control step PB001, a value derived by subtracting the qualitythreshold value Rth from the reception quality Rq [dB] measured in themobile station is replaced with the control amount ΔA [dB]. At controlstep PB002, ΔA is subtracted from the base station transmission powermobile station management value Pmbs [dBW]. At control step PB003, bycombining the value of the base station transmission power mobilestation management value Pmbs and the minimum propagation loss basestation index Bpmi, the transmission power control information symbolSpct is generated. Then, the transmission power control informationsymbol Spct is output to the transmission power control informationsymbol inserting portion 17 shown in FIG. 1.

Next, discussion will be given for the transmission power controlportion 27 in the base station corresponding to the mobile station.

FIG. 10 is an illustration showing a construction of the transmissionpower control portion 27 of the base station corresponding to thetransmission power control information symbol generating portion 12shown in FIG. 9.

At first, at control step CC001, the minimum propagation loss basestation index Bpmi and the base station transmission power mobilestation management value Pmbs are separated. Then, at control stepCC002, check is performed whether the minimum propagation loss basestation index Bpmi and the own base station index are equal to eachother or not. If the minimum propagation loss base station index Bpmiand the own base station index are consistent, the control value Pctl ofthe variable output amplifier 29 is set as the base station transmissionpower mobile station management value Pmbs, at control step CC003.Otherwise, the control value Pctl is set at the minimum base stationtransmission power Pmin at control step CC004. Subsequently, the controlvalue Pctl is output to the variable output amplifier 29 at control stepCC005.

By the shown embodiment, since sequential transmission power controlaccording to power increasing and decreasing command from the mobilestation is not performed, a problem of accumulation of error inincreasing and decreasing control of the base station transmission powerwhich should be caused in the former embodiment, can be avoided.

Further different construction of the transmission power control symbolgenerating portion 12 in the mobile station shown in FIG. 9 isillustrated in FIG. 11. In the shown embodiment, similarly to thetransmission power control symbol generating portion 12 shown in FIG. 9,the mobile station constantly transmit the base station transmissionpower value and the minimum propagation loss base station index.However, concerning setting of the base station transmission powervalue, control of increasing or decreasing of a given power controlamount to and from the current transmission power value is performeddepending upon result of comparison between the reception quality Rq andthe given quality threshold value Rth.

At control step PC001, comparison of the measured reception quality Rq[dB] and the quality threshold value Rth [dB] in the mobile station isperformed. When the reception quality Rq is greater than the qualitythreshold value Rth, the power attenuation amount ΔPd [dB] is subtractedfrom the current base station transmission power mobile stationmanagement value Pmbs [dBW] at control step PC003. If the receptionquality Rq is smaller than the quality threshold value Rth, the powerincreasing amount ΔPu [dB] is added to the current base stationtransmission power mobile station management value Pmbs [dBW] at controlstep PC002. The value of the base station transmission power mobilestation management value Pmbs is combined with the minimum propagationloss base station index Bpmi to be output as the transmission powercontrol information symbol Spct at control step PC002. In the shownembodiment of the mobile station, the base station transmission powercontrol system according to the present invention enables soft hand overoperation with the base station having the transmission power controlportion 27 shown in FIG. 10, is incorporated.

A still further embodiment of the mobile station and the base stationaccording to the present invention, particularly the embodiment, inwhich the transmission power control information symbol generating means12 and the transmission power control portion 27 are modified, will bediscussed. The shown embodiment is directed to the base station powertransmission system employing a construction, in which the minimumpropagation loss base station index is constantly transmitted from themobile station to the base station. In the shown embodiment, the minimumpropagation loss base station index is transmitted intermittently.

FIG. 12 shows one embodiment of the mobile station intermittentlytransmitting the minimum propagation loss base station index, andillustrates a construction of the transmission power control symbolgenerating portion 12 transmitting the minimum propagation loss basestation index only when variation thereof occurs.

At control step PC001, comparison of the reception quality Rq [dB]measured in the mobile station and the quality threshold value Rth ismade. As a result of comparison, if the reception quality Rq [dB] isgreater than the quality threshold value Rth [dB], a transmission powercontrol bit Pbt is set to 0 at control step PC002. On the other hand,when the reception quality Rq [dB] is smaller than the quality thresholdvalue Rth [dB], the transmission power control bit Pbt is set to 1, atcontrol step PC003. Next, at control step PC004, reference is made tothe minimum propagation loss base station index Bpmi. If the minimumpropagation loss base station index Bpmi is equal to the precedingminimum propagation loss base station, the transmission power controlinformation symbol Spct is set at a value equal to Pbt. Then,transmission power control information symbol Poct of one bit is outputto the transmission power control information symbol inserting portion17 of FIG. 1. On the other hand, when the minimum propagation loss basestation index represents the base station different from the minimumpropagation loss base station, the transmission power controlinformation symbol Spct is set according to the following equation (2)to output the transmission power control information symbol Spct of twoor more bits to the transmission power control information symbolinserting portion 17 of FIG. 1, at control step PC006.Spct=2×Bpmi+Pbt  (2)

In the shown embodiment, when the minimum propagation loss base stationis varied, the control bit consisted of two or more bits with containingthe base station index Bpmi in the transmission power controlinformation symbol Spct, is transmitted. On the other hand, when theminimum propagation loss base station is not varied, only control bitconsisted of one bit is transmitted to the base station to reducetransmission amount of the transmission power control information.

FIG. 13 is an illustration showing a construction of the transmissionpower control portion 27 in the base station according to the presentinvention corresponding to the transmission power control informationsymbol generating portion 12 shown in FIG. 12.

In the shown embodiment, at control step CD001, check is performedwhether the transmission power control information Spcr is consisted oftwo or more bits or not. If the transmission power control informationSpcr is consisted of two or more bits, the control bit Pbt and theminimum propagation loss base station index Bsi are obtained accordingto the following equations (3) and (4) at control step CD002.Pbt=Spcr mod 2  (3)Bsi=int (Spcr/2)  (4)

wherein X mod Y is a remainder of division of X by Y and int (X)represents cut off integer. The equations (3) and (4) are equivalent toa process separating two bit control bit.

At control step CD002, after obtaining Pbt and Bsi, check is performedwhether the minimum propagation loss base station index Bsi is equal tothe own base station index or not at control step CD004. If the minimumpropagation loss base station index Bsi is equal to the own base stationindex the transmission flag Fst is set to 1 at control step CD005, andotherwise, the transmission flag Fst is set to 0 at control step CD006.Here, the initial value of the transmission flag Fst is 0. Thetransmission flag Fst as set is maintained until next change.

On the other hand, at control step CD001, when the transmission powercontrol information Spcr is not consisted of two or more bits, thecontrol bit Pbt is set to a value equal to the value of the transmissionpower control information Spcr. After control step CD003, as the valueof the transmission flag Fst, the preceding value is used as it is.

Next, at control step CD007, check is performed whether the control bitPbt is 0 or not. If the control bit Pbt is 0, the power attenuationamount ΔPd [dB] is subtracted from the base station transmission powerPbsm [dBW] at step CD009. If the transmission power control informationSpcr is not 0, the power increasing amount ΔPu [dB] is added to the basestation transmission power Pbsm [dBW] at control step CD008. The controlvalue Pctl [dbw] of the variable output anplifier 29 is calculated bythe equation (1) to be output to the anplifier 29 at control step CD010.

FIG. 14 shows a yet further embodiment of the mobile stationintermittently transmitting the minimum propagation loss base stationindex, in which the transmission power control information symbolgenerating portion 12 corresponding to the base station transmissionpower control portion 27 shown in FIG. 13 has different construction. Inthe shown embodiment, review of the transmission power of the primarybase station is performed regularly to regularly transmit the minimumpropagation loss base station index.

At control step PD001, comparison of the reception quality Rq [dB]measured in the mobile station and the equality threshold value Rth isperformed. As a result of comparison, if the reception quality Rq [dB]is greater than the quality threshold value Rth [dB], at control stepPD002, the transmission power control bit Pbt is set to 0. If thereception quality Rq [dB] is smaller than the quality threshold valueRth [dB], at control step PD003, the transmission power control bit Pbtis set to 1. Next, at control step PD004, check is performed whether acurrent timing is a timing for effecting review of the primary basestation or not. If the current timing is the reviewing timing, atcontrol step PD006, the transmission power control information symbolSpct is set according to the foregoing equation (2). If the currenttiming is not the reviewing timing, the transmission power controlinformation symbol Spct is set to be equal to Pbt at control step PD005.The transmission power control information symbol Spct determined ateither step of PD005 or PD006 is output to the transmission powercontrol information symbol inserting portion 17 of FIG. 1.

FIG. 15 shows a construction which is differentiated in the transmissionpower control portion 27 of the base station corresponding to thetransmission power control information symbol generating portion 12shown in FIG. 12 or 14. In the shown embodiment, as the control valuePctl of the transmission power, increasing and decreasing control of thegiven power control amount for the current control value is performed.

At control step CE001, check is performed whether the transmission powercontrol information Spcr is consisted of two or more bits. If thetransmission power control information Spcr is consisted of two or morebits, the control bit Pbt and the minimum propagation loss base stationindex Bsi are obtained according to the foregoing equations (3) and (4)at control step CE002. After obtaining Pbt and Bsi at step CE002, checkis performed whether the minimum propagation loss base station index isequal to the own base station index or not. When the minimum propagationloss base station index Bsi is equal to the own base station index, thetransmission flag Fst is set at control step CE005. Otherwise, thecontrol flag Fst is set 0 at control step CE006. Here, the initial valueof the transmission flag Fst is 0, the value of the set transmissionflag is constantly held as is until next change.

On the other hand, when the transmission power control information Spcris judged as being consisted of two or more bits at control step CE001,the control bit Pbt is set at a value equal to the transmission powercontrol information Spcr at control step CE003. After control stepCE003, as the value of the transmission flag Fst, the preceding value isused.

Next, check is performed whether Pbt is 1 or not at control step CE007.If Pb is 1, check is performed whether Fst is 1 or not at control stepCE008. If both of the control bit Pbt and the transmission flag Fst are1, the power increasing amount ΔPu [dB] is added to the base stationtransmission power Pbsm [dBW] at control step CE009. Otherwise, thepower attenuation amount ΔPd [dB] is subtracted from the base stationtransmission power Pbsm [dBW] at control step CE010. The value of basestation transmission power Pbsm is replaced with Pctl and output to thevariable output amplifier 29.

The base station transmission power control system according to thepresent invention is constructed by the mobile station having thetransmission power control information symbol 12 shown in FIG. 12 or 14and the base station having the transmission power control portion 27shown in FIG. 13 or 15.

As yet further embodiment of the present invention, a construction,discussion will be given for the mobile station and the base station,and more particularly for the construction, in which the transmissionpower control information symbol generating portion 12 and thetransmission power control portion 27 are differentiated.

FIG. 16 is an illustration of the yet further embodiment of the mobilestation according to the present invention, and particularly showing thetransmission power control information symbol generating portion 12. Theshown embodiment is premised to synchronous operation with the basestation and is adapted to normally transmit only control informationdesignating increasing and decreasing of the transmission power of thebase station as the transmission power control signal and regularlytransmit only primary base station information as the transmission powercontrol signal.

At control step PE001, comparison of the reception quality Rq [dB]measured in the mobile station and the quality threshold value Rth isperformed. As a result of comparison, if the reception quality Rq [dB]is greater than the quality threshold value Rth [dB], the transmissionpower control bit Pbt is set at 0 at control step PE002. On the otherhand, if the reception quality Rq [dB] is smaller than the qualitythreshold value Rth [dB], the transmission power control bit Pbt is setat 1 at control step PE003. Next, at control step PE004, check isperformed whether the current timing is the primary base stationreviewing timing or not. If the current timing is the primary basestation reviewing timing, the transmission power control informationsymbol Spct is set to be equal to minimum propagation loss base stationindex Bpmi at control step PR006. On the other hand, if the currenttiming is not the primary base station reviewing timing, thetransmission power control information symbol Spct is set to be equal toPbt at control step PE005. The transmission power control informationsymbol Spct determined at control step PE005 or PE006 is output to thetransmission power control information symbol inserting portion 17 ofFIG. 1.

FIG. 17 is an illustration showing a construction of the transmissionpower control portion 27 in the base station according to the presentinvention corresponding to the transmission power control informationsymbol generating portion 12 shown in FIG. 16. In the shown embodiment,transmission power restriction control is performed in synchronism withthe primary base station information to be regularly transmitted fromthe mobile station to output the control value Pctl.

At first, at control step CF001, check is performed whether the currenttiming is the primary base station reviewing timing. Here, the reviewingtiming of the primary base station of respective mobile station and thebase station are established synchronization with each other. When thecurrent timing is judged as primary base station reviewing timing aschecked at control step CF001, the transmission power control bit Pbt isset to be equal to the transmission power control information symbolSpcr at control step CF003. Then, at control step CF007, check isperformed whether Pbt is 0 or not. If Pbt is 0, the power attenuationamount ΔPd [dB] is subtracted from the base station transmission powerPbsm [dBW] at control step CF009. If Pbt is not 0, the power increasingamount Δ Pu [dB] is added to the base station transmission power Pbsm[dBW] at control step CF008.

After determining the base station transmission power Pbsm at controlstep CF005 or CF006, the control value Pctl [dBW] of the variable outputamplifier is derived by the foregoing formula (1) at control step CF010for outputting the control value Pctl to the variable output amplifier29 of FIG. 2.

On the other hand, when judgment is made whether the current timing isthe primary base station reviewing timing at control step CF001, theminimum propagation loss base station index Bsi and the transmissionpower control information symbol Spcr are set to be equal to each otherat control step CF002. Also, check is performed whether Bsi is equal tothe own base station index at control step CF004. When judgment is madethat Bsi is equal to the own base station index, the transmission flagFst is set at 1 at control step CF005. Otherwise, Fst is set at 0 atcontrol step CF006. Here, the initial value of the transmission flag Fstis 0 and the set transmission flag is maintained as is until occurrenceof next change.

After determination of the transmission flag Fst at control step CF005or CF006, the control value Pctl [dBW] of the variable output amplifier29 is derived by the foregoing formula (1) at control step CF010. Then,Pctl is output to the variable output amplifier 29 of FIG. 2.

FIG. 18 shows an another embodiment of the base station of the presentinvention. The shown embodiment is particularly differentiated in thetransmission power control portion 27 corresponding to the transmissionpower control shown in FIG. 16. The shown embodiment is adapted toperform increasing and decreasing control for the control value Pctl ofthe transmission power with a given power control amount relative to thecurrent control value.

At control step CG001, check is performed whether the current timing isthe primary base station reviewing timing or not. Here, the primary basestation reviewing timings in respective of the mobile station and thebase station are assumed to be synchronized with each other. At controlstep CG001, if the current timing is judged as the primary base stationreviewing timing, the minimum propagation loss base station index Bsi isset equal to the transmission power control information symbol Spcr atcontrol step CG002. Also, at step CG004, check is performed whether thebase station index of own station is equal to BSi. If judgment is madethat BSi is equal to the base station index of own station, thetransmission flag Fst is set to 1 at control step CG005, and otherwise,the transmission flag Fst is set to 0 at control step CG006. Here, theinitial value of the transmission flag Fst is 0, and set transmissionflag is maintained until next change.

After determination of the transmission flag Fst at control step CG005or CG006, the control value Pctl [dBW] of the variable output amplifier29 is set equal to Pbsm at control step CG011. Then, the control valuePctl is output to the variable output amplifier 29 of FIG. 2.

On the other hand, at control step CG001, if the current timing is notjudged as the primary base station reviewing timing, the transmissionpower control bit Pbt is set to be equal to the transmission powercontrol information symbol Spcr at control step CG003. Check isperformed whether Pbt is 1 or not at control step CG007.

If judgment is made that Pbt is not 1 at control step CG007, the powerattenuation amount ΔPd [dB] is subtracted from the base stationtransmission power Pbsm at control step CG010. On the other hand, ifjudgement is made that Pbt is 1 at control step CG007, check isperformed whether the transmission flag Fst is 1 or not at control stepCG008. If Fst is not 1, the power attenuation amount ΔPd [dB] issubtracted from the base station transmission power Pbsm at control stepCG010. On the other hand, when Fst is 1, the power increasing amount ΔPu[dB] is added to the base station transmission power Pbsm [dBW] atcontrol step CG009. After determination of the transmission flag Fst atcontrol step CG009 or CG010, the control value Pctl [dBW] of thevariable output amplifier 29 is set to be equal to Pbsm. Then, Pctl isoutput to the variable output amplifier 29 of FIG. 2.

The base station transmission power control system according to thepresent invention is constructed with the mobile station having thetransmission power control information symbol generating portion 12shown in FIG. 16 and the base station having the transmission powercontrol portion 27 shown in FIGS. 17 and 18.

With transmission power control method according to the presentinvention, by restricting output of the base stations other than theprimary base station, in which the propagation loss with the mobilestation is minimum, interference for the peripheral mobile stations canbe reduced in comparison with the conventional transmission powercontrol method. As a result, high down link capacity can be obtained.

On the other hand, by restricting the transmission power of the basestations other than the primary base station during soft hand over,increasing of interference of down link due to a plural base stationtransmission which raises problem of soft hand over, can be avoided.

Furthermore, since the transmission power control system according tothe present invention is premised to application of soft hand over,connection between the mobile station and the minimum propagation lossbase station is guaranteed even when hand over control delay is present.Accordingly, transmission of the excessive transmission power of theformer base station connected before hand over due to hand over delay,can be avoided.

In the foregoing transmission power control system according to thepresent invention, in order to realize selection of the primary basestation, the mobile station uses the base station number of the primarybase station as the transmission power control signal. When increasingof the transmission power is to be demanded to the base station, themobile station transmits the base station number of the primary basestation. On the other hand, when decreasing of the transmission power isto be demanded, the mobile station transmits a dedicated number. On theother hand, during soft hand over, each base station increasestransmission power when the own base station number is transmitted, anddecreases otherwise. Particularly, when the base station number otherthan own base station is transmitted, the transmission power isrestricted to the minimum power abruptly.

Next, observation is made for the case of transmission power controlaccording to the system according to the present invention. Soft handover is essential technology for realizing communication with theminimum propagation loss base station in the real system, in which handover control delay cannot be ignored. Concerning the down link, since aplurality of base stations have to perform transmission to one mobilestation, interference for the mobile station is inherently increased. Ascan be clear from comparison of FIGS. 19 and 34, all base stations areconstantly performing transmission during soft hand over in theconventional transmission power control system with taking the basestation transmission power of FIG. 34, whereas, in the shown embodiment,only minimum propagation loss base station performs transmission andother base stations are restricted the transmission power to the minimumtransmission power. By this, the problem of increasing of interferenceby the plural base station transmission as in the soft hand over, can besuccessfully avoided.

However, the shown embodiment of the system, in which the serial numberof the primary base station is utilized as the transmission powercontrol signal, causes error in selection of the base station whenreception error is caused in the transmission power control signal.Then, as in the timing T0′ [sec] and T1′ [sec] of the dotted link inFIG. 19, the state where the transmission powers of both of the basestations become minimum transmission power, is frequently caused. Thisphenomenon is considered to be caused by abrupt restriction of theoutput to the minimum transmission power value when the base stationnumber identifying the base station other than own base station isreceived as the transmission power control signal. Namely, it isfrequently caused that, despite of the fact that when reception error inreception of the transmission power control signal is caused, the basestation number of own base station is transmitted, the base stationerroneously make judgment that the base station number of other basestation is transmitted to make all base stations to transmit the minimumtransmission power during soft hand over as observed in FIG. 19. In thiscase, in the mobile station, reception quality is significantly degradeddue to lowering of the reception intensity of the desired signal.

A further embodiment of the present invention for solving the foregoingproblem will be discussed hereinafter. Referring to FIG. 20, thetransmission signal transmitted from the base station is received viathe transmission and reception common unit 1, the RF portion 2 and thedemodulation circuit 3, and is measured the reception quality Rq [dB] bythe reception quality measuring unit 4. The reception quality obtainedvia the demodulation circuit 3 and the reception quality measuring unit4 represents composite quality of the signal from a plurality of basestations during soft hand over. On the other hand, the pilot signaltransmitted from each base station and contained in the output of the RFportion 2 during soft hand over is measured the pilot receptionintensity Pr,i in the pilot signal reception intensity measuring unit 5.Here, i represents the number of the base station during soft hand over,which will be discussed in detail with reference to FIGS. 24 to 27. Forthe base stations, serial integer values starting from 1 is assignedduring soft hand over.

When the base station number equal to different base station isassigned, a composite value of the reception levels of the pilot signalstransmitted from the respective base stations is taken. Assignment ofeach base station number is determined in the base station numberinformation portion 13 with reference to the output value of the RFportion 2 and output as the base station number assignment informationBSNCI.

The reception quality Rq and the pilot reception intensity Pr,i areinput to the transmission power control information symbol generatingportion 12. The transmission power control information symbol generatingportion 12 generates the transmission power control information symbolSpct for the base station. The transmission power control informationsymbol Spct is coupled with the transmission signal output from thetransmission information portion 11 and the base station numberassignment information BSCI as output of the base station numberinformation portion 13, in the data coupling portion 6. It should beappreciated that when the base station number assignment informationBSNCI is “NULL”, coupling of the base station number assignmentinformation is not performed. Furthermore, the output signal of the datacoupling portion 6 is inserted the overhead information in the overheadinserting portion 10. When the transmission information, thetransmission power control information, the overhead information and thebase station assignment information are contained, the transmissionsignal containing such information is transmitted to the base stationvia the spreading portion 9, the modulator 8, the amplifier unit 7 andthe transmission and reception common unit 1.

FIG. 21 is an illustration showing a construction of the shownembodiment of the base station. The transmission signal containingtransmission power control information transmitted from the mobilestation shown in FIG. 20 is transmitted to the transmission powercontrol symbol detector 26 via the transmission and reception commonunit 21, the RF portion 22, the frequency down converter 23, thedespreading portion 24, and the reception data demodulator 25. Then, thetransmission power control symbol detector 26 detects the transmissionpower control information Spcr. The transmission power controlinformation Spcr is input to the transmission power control portion 27.The transmission power control portion 27 outputs the control value Pctlso that the output level [dBW] of the variable output amplifier 29becomes a value reflecting the transmission power control informationSpcr on the basis of the transmission power control information Spcr.The transmission signal to the mobile station output from thetransmission spreaded RF signal portion 28 is amplified by the variableoutput amplifier 29 controlled by the signal Pctl and transmitted to themobile station via the transmission and reception common unit 21.

On the other hand, the output of the reception data demodulator 25 isinput to the base station number detector 30. In the base station numberdetector 30, the own base station assignment number i transmitted fromthe mobile station is detected. However, the base station numberassignment information from the mobile station is not transmitted,varying of the base station number is not performed.

FIGS. 22, 23 and 24 are flowcharts of one embodiment of signalprocessing of the transmission power control information symbolgenerating portion 12 of the mobile station, the transmission powercontrol portion 27 of the base station and the base signal numberinformation portion 13 in the mobile station. At first, in the mobilestation shown in FIG. 22, operation of the transmission power controlinformation symbol generating portion 12 will be discussed. Thereception quality Rq measured in the mobile station is compared with thequality threshold value Rth [dB] in control step PF001. As a result ofcomparison, if Rq>Rth, the transmission power control information symbolSpct is set to a dedicated information “0” representative of powerdecreasing command at control step PF002. Otherwise, Spct is set to thebase station number i, at which the pilot reception intensity Pr,imeasured in the pilot signal reception intensity measuring unit 5becomes maximum at control step PF003. Then, at control step PF004, anyof the transmission power control information symbol Spct is output.

Next, discussion will be given for operation of the transmission powercontrol portion 27 in the base station shown in FIG. 23. Thetransmission power control information Spcr detected by the transmissionpower control symbol detector 26 is judged whether the transmissionpower control information Spcr is “0” at control step CH001. If thetransmission power control information Spcr is not “0”, the given powerincreasing amount ΔPu [dB] is added to a current virtual base stationtransmission power Pbsm [dBW] directed to the mobile station whichtransmitted the transmission power control information Spcr at controlstep CH002. On the other hand, when the transmission power controlinformation Spcr is “0”, the given power attenuation amount ΔPd [dB] issubtracted from the virtual base station transmission power Pbsm atcontrol step CH003. It should be noted that the value of the virtualbase station transmission power Pbsm is held as the updated value in thepreceding timing. After variation of the virtual base stationtransmission power Pbsm at control step CH002 or CH003, Pbsm isrestricted so that it falls within a range of a maximum transmissionpower Pmax and the minimum transmission power Pmin at control stepCH007.

After control step CH007, check is performed whether the transmissionpower control information Spcr is consistent with the base stationnumber of own base station at control step CH004. If Spcr is consistentwith the base station number of the own base station, the control valuePctl is set so that the output of the variable output amplifier 29 shownin FIG. 21 becomes Pbsm at control step CH005. On the other hand, whenthe transmission power control information Spcr is not consistent withthe base station number of the base station, a control value ΔPd.corresponding to the given power attenuation amount is subtracted fromthe control value Pctl at control step CH006. The value of the controlvalue Pctl is held at a value updated in the preceding timing.

The control value Pctl obtained at control step CH005 or CH006 isrestricted so that the transmission power is smaller than the minimumtransmission power Pmin at control step CH008. Thereafter, thetransmission power is output to the variable output amplifier 29. Thebase station transmission power is controlled to the power correspondingto the control value Octl by the variable output amplifier 29.

Next, discussion will be given for an example of operation of the basestation number information 13 in the mobile station shown in FIG. 24,and of assignment of the base station number i for the base stationperforming soft hand over. At first, at control step NA001, check isperformed whether soft hand over base station is varied or not. Ifvariation is not caused, “Null” namely nil information is set as thebase station number assignment information BSCNI at control step NA004.On the other hand, when judgement is made that the soft hand over basestation is varied at control step NA001, the reception intensity of thepilot signal transmitted from the new soft hand over base station ismeasured from the output signal of the RF portion 2 at propagation lossmeasuring step NA002. Furthermore, by this pilot reception intensity,propagation losses LSk from the mobile station to respective basestations are estimated. Here, k represents unique base station number ofthe base station during soft hand over.

At propagation loss measuring step NA002, the propagation loss LSk isinput to control step NA003 for temporarily assigning the base stationnumber i to respective base stations k during soft hand over at controlstep NA003. Concerning the base station number i=i0, all of the basestations satisfying the following formula (5) is assigned. Here, i0 isas number not dedicated number “0” of the power decreasing command.LSk≦PMBSth  (5)wherein PMBSth represents a propagation loss threshold value.

When the transmission power control information symbol Spct is actuallytransmitted, a bit string consisted of several bits is used. The basestation group satisfying the foregoing formula (5) is the base stationgroup having small propagation loss to the mobile station. Namely, thereis high probability that the base station number i=i0 of these basestation group is selected as the transmission power control informationsymbol Spct when the mobile station demands increasing of thetransmission power. On the other hand, when the mobile station demandsdecreasing of the transmission power, the dedicated number “0” forcommanding decreasing of the power is constantly selected at controlstep PF002 of FIG. 22. Therefore, the transmission power control bitstring expressing respective of the base station number i=i0 of the basestation group satisfying the foregoing formula (5) and the dedicatednumber “0” representative of the power decreasing command is set to havelarge number of different bits in order to prevent erroneous detectionthe other.

FIG. 25 shows an embodiment of setting of the transmission power controlbit string to be actually transmitted in the case where the base stationnumber i=i0 and the dedicated number “0” indicative of the powerdecreasing command are used as the transmission power controlinformation symbol Spct. Here, the transmission power control bit isassumed to be consisted of three bits.

For the base station not satisfying the foregoing formula (5), mutuallydistinct base station number i=ij is assigned. Here, ij is the numbernot “0” and not “i0”. The base station number assignment informationBSNCI determined at control step NA003 or NA004 is input to the datacoupling unit 6 shown in FIG. 20.

In the base station transmission power control shown in FIG. 23, thecontrol value Pctl of the variable output amplifier 29 is continuouslyattenuated at a rate of “ΔPd” unless the base station number of own basestation is transmitted as the transmission power control signal, toreach the minimum transmission power value Pmin. Then, the transmissionpower is maintained at the minimum transmission power value Pmin.Namely, when the mobile station transmits the base station number, inorder to transmit the base station number of the primary base station,the transmission power of non-primary base station is maintained at theminimum transmission power Pmin. By this, problem of interference whichis caused by simultaneous transmission of a plurality of base stations,can be avoided to achieve high down link capacity. On the other hand,upon restriction of the transmission power of the base station otherthan the primary base station, instead of restricting the transmissionpower abruptly, the transmission power is moderately attenuated at arate “ΔPd”. Thus, even when error is caused in selection of the basestation, abrupt lowering of the desired reception field intensity in themobile station is not caused to prevent significant degradation of thereception quality observed in the former embodiment shown in FIG. 19 canbe prevented.

Since the virtual base station transmission power Pbsm is increased whenthe base station number is transmitted as the transmission power controlsignal, the condition of the minimum transmission power value Pmin asPctl is not maintained for long period. The virtual base stationtransmission power Pbsm teaches a set target value of the control valuePctl in the case where the own base station number is transmitted afternot transmitting the base station number of own base station for a whileand serves for preventing degradation of quality of the desired signal.The virtual base station transmission power Pbsm is maintained at equalvalue in any base station during soft hand over so far as receptionerror is not present in the transmission power control signal and itsinitial values are equal.

On the other hand, by assigning the base station number equal to thebase station group satisfying the formula (5), transmission by severalbase stations having small propagation loss including the base station,in which the propagation loss to the mobile station becomes minimum, canbe achieved. When the transmission powers transmitted from several basestations are controlled at substantially equal value, the signals fromany base stations are received at substantially equal receptionintensity in the mobile station to improve communication quality.

FIG. 26 is an illustration showing other embodiment of the base stationnumber information portion 13 in the mobile station, like elements tothose in FIG. 24 will be identified by like reference numerals. Atfirst, at control step NA001, check is made whether soft hand over basestation is varied or not. The soft hand over base station is not variedat control step NA004, “Null” namely nil information is set as the basestation number assignment information BSNCI at control step NA004. Whenjudgment is made that soft hand over base station is varied as checkedat control step NA001, the base station number i=ij different from eachbase station is assigned at control step NA006. Here, ij is other thandedicated number “0” representative of the power decreasing command. Theoutput signal of the RF portion 2 is not used in the shown embodimentand is terminated (step NA005).

As set forth above, in the shown embodiment, since measurement of thepropagation loss (NA002) as required in the embodiment shown in FIG. 24becomes unnecessary, construction of the mobile station can besimplified.

FIG. 27 is an illustration showing another embodiment of the basestation number information portion 13 in the mobile station. Likeelements to those in FIG. 24 will be identified by like referencenumerals. At first, at propagation loss measuring step NA002, receptionintensity of the pilot signal transmitted from the base station duringsoft hand over is measured from the output signal of the RF portion 2.Furthermore, on the basis of reception intensity of the pilot signal,propagation loss LSk from the mobile station to the base station in softhand over is estimated. k is unique base station number in soft handover of all base stations in the system.

At control step NA007, check is performed whether the base station ofthe minimum propagation loss is varied or not on the basis of thepropagation loss LSk. If the base station of the minimum propagationloss is not varied, further check is performed at control step NA001whether the soft hand over base station is varied. If the soft hand overbase station is not varied, “Null” namely nil information is set as thebase station number assignment information BSNCI at control step NA004.

When the base station of the minimum propagation loss is varied aschecked at control step NA007 or when the soft hand over base station isvaried as checked at control step NA001, the base station numbers areassigned temporarily to respective of base stations (assigned the basestation number k) in soft hand over in the similar manner as that atcontrol step NA003 of FIG. 24. In the embodiment of FIG. 24, only whenthe soft hand over base station is varied, base station numberassignment process is performed. In contrast to this, in the shownembodiment of FIG. 27, even when the base station of minimum propagationloss is varied, variation of assignment of the base station number isperformed. By this, the base station number i=i0 which is difficult tobe erroneously detected as the power decreasing number “0”, can be setfor the base station having small propagation loss to the mobile stationand constantly satisfying the foregoing formula (5). Accordingly,accurate transmission power control becomes possible.

The operation of the shown embodiment of the base station transmissionpower control system will be discussed with reference to FIG. 28. FIG.28 illustrates time transition PTP-A and PTP-B of the transmission powerin each base station in the case where the embodiment of the basestation number information portion 13 shown in FIG. 26 is applied. InFIG. 28, the vertical axis represents a base station transmission power[dBW] and the horizontal axis represents a time [sec]. FIG. 28corresponds to FIG. 34 showing the result obtained by the conventionaltransmission power control system and FIG. 19 showing the result of theformer embodiment. The propagation loss threshold value PMBSth isassumed as 1, respective base station number 1 and 2 are assigned forrespective base stations BS-A and BS-B during observation period shownin FIG. 28, in which soft hand over base station is not varied. In FIG.28, the solid link shows the case where reception error in receiving thetransmission power control signal is not caused and the dotted linkshows the case where reception error in receiving the transmission powercontrol signal is caused.

In the shown embodiment of the transmission power control method shownin FIG. 28, during a period from a timing T0 [sec] to T1 [sec], the basestation BS-B exclusively perform transmission as shown by time dependentvariation PTP-B. Then, the base station BS-A performs transmission withminimum transmission power. Upon switching of the base station at thetiming T1, instead of instantly attenuating the transmission power ofthe former base station connected before switching to the minimum value,the transmission power is moderately attenuated over a period of timingT1D to T1 [sec].

During the period from T1 to T2 of the time dependent variation PTP-B,there is shown an occurrence of temporary increase of the transmissionpower. This is caused by erroneous selection of the base station byreception error of the transmission power control signal. However, thetransmission power is quickly attenuated, continuous excess or lackingof the transmission power as observed in FIG. 34, is not observed.

On the other hand, in FIG. 24, the problem that the transmission powerof all of the base stations become minimum transmission power duringsoft hand over as observed in the former embodiment of FIG. 19, can beavoided, and thus occurrence of significant degradation of the receptionquality due to lowering of the reception intensity of the desired signalin the mobile station can be avoided.

In the transmission power control method shown in FIG. 19, both of twobase stations BS-A and BS-B constantly output transmission waves withoutrestriction. On the other hand, as shown in FIG. 28, in the shownembodiment of the transmission power control system, one of the basestations is selected depending upon the reception level of the pilotsignal received by the mobile station. Then the selected one of the basestation outputs the transmission wave, and output of the transmissionwave of the other base station is restricted. Namely, by the shownsystem, a plural base station transmission causing problem in down linkduring soft hand over can be avoided to suppress interference.

Another embodiment of transmission method of the transmission powercontrol information (TPC) symbol Spct generated in the transmissionpower control information symbol generating portion 12 of the mobilestation will be discussed with reference to FIG. 29. A transmissionframe is consisted of four time slots. As shown by hatching, the leadingtime slot is consisted of the pilot signal (PILOT), a base stationidentification number information (BS-ID) of two bit as the base stationindex and the transmission information (DATA). On the other hand, eachof remaining three time slots is consisted of the pilot signal (PILOT),two bit transmission power control information (TPC) and transmissioninformation (DATA).

The transmission power control information (TPC) uses respective twobits of three time slots, respectively. On the other hand, the basestation identification number information (BS-ID) represents one basestation index with total 8 bits of respective 2 bits of four time slotsas shown by hatching.

By the foregoing embodiment, upon restricting transmission power of thebase station other than the base station having small propagation losswith the mobile station among the base station group during soft handover, the transmission power is not restricted abruptly but ismoderately attenuated. Thus, even when error is caused in selection ofthe base station, abrupt lowering of reception intensity of the desiredwave in the mobile station can be avoided.

On the other hand, instead of assigning transmission for all basestations during soft hand over, one or several base stations areassigned for transmission for reducing influence of transmission byinappropriate transmission power due to reception error of thetransmission power control signal by the effect of spatial diversity. Onthe other hand, when each base station manages the virtual base stationtransmission power value and set as set target of the output value ofthe transmission power value in new base station upon switching ofassignment of the base station assigned for transmission, degradation ofquality or excessive quality in the mobile station can be successfullyprevented.

Furthermore, by performing transmission to the mobile station fromlimited number of base stations instead of all base stations during softhand over, interference of down link can be eliminated. From the resultset forth above, by application of the transmission power control systemaccording to the present invention, high down link capacity can beachieved.

Although the present invention has been illustrated and described withrespect to exemplary embodiment thereof, it should be understood bythose skilled in the art that the foregoing and various other changes,omissions and additions may be made therein and thereto, withoutdeparting from the spirit and scope of the present invention. Therefore,the present invention should not be understood as limited to thespecific embodiment set out above but to include all possibleembodiments which can be embodied within a scope encompassed andequivalents thereof with respect to the feature set out in the appendedclaims.

1. A mobile station in a code division multi access cellular mobileradio communication system comprising a plurality of base stationsrespectively announcing unique pilot signals, said mobile station beingcapable of simultaneously establishing connection with a soft hand overbase station group comprising some of base stations out of saidplurality of base stations in the system, said mobile stationcomprising; a primary base station detecting means for detecting primarybase station which transmits a pilot signal of the maximum receptionlevel at said mobile station among received pilot signals from said basestations in said soft hand over base station group; a base stationtransmission power control signal determining means for setting a basestation transmission power control signal indicating to increase ordecrease a transmission power; and a control signal transmitting meansfor transmitting primary base station information detected by saidprimary base station detecting means and said base station transmissionpower control signal determined by said base station control signaldetermining means to said base station group in soft hand over.
 2. Amobile station according to claim 1, said mobile station furthercomprising a reception quality detecting means for detecting acommunication reception quality, wherein said base station transmissionpower control signal determining means sets the base stationtransmission power control signal for increasing the transmission powerin the event that the communication reception quality detected by saidreception quality detecting means does not exceed a desired quality andsets the base station transmission power control signal for decreasingthe transmission power in the event that the communication receptionquality detected by said reception quality detecting means exceeds adesired quality.
 3. A mobile station according to claim 1, wherein saidcontrol signal transmitting means continuously transmits said basestation transmission power control signal determined by said basestation control signal determining means to the base station group insoft hand over or intermittently transmits the primary base stationinformation detected by said primary base station detecting means andsaid base station transmission power control signal determined by saidbase station control signal determining means to said base station groupin soft hand over.
 4. A mobile station according to claim 1, said mobilestation further comprising a reception quality detecting means fordetecting a communication reception quality, wherein said base stationtransmission power control signal determining unit sets the base stationtransmission power control signal for increasing the transmission powerin the event that the communication reception quality detected by saidreception quality detecting unit does not exceed a desired quality andsets the base station transmission power control signal for decreasingthe transmission power in the event that the communication receptionquality detected by said reception quality detecting unit exceeds adesired quality.
 5. A base station transmission power control system ina code division multi access cellular mobile radio communication system,said communication system comprising: a plurality of base stationsrespectively announcing unique pilot signals and a mobile station whichis capable of simultaneously establishing connection with a soft handover base station group comprising some of base stations out of saidplurality of base stations, said mobile station detects a primary basestation, a reception level of a pilot signal received from the primarybase station is maximum level among reception levels of pilot signalsreceived from respective base stations in soft hand over base stationgroup, said mobile station sets one of a power increasing symbol and apower decreasing symbol in said transmission power control bit, andtransmits said transmission power control bit and primary base stationinformation to said soft hand over base station group, and each basestation of said soft hand over base station group receives atransmission power control signal which includes said primary basestation information, and restricts a transmission power of atransmission signal to the mobile station in the event that said primarybase station information is not consistent with a base stationinformation of said base stations.
 6. A base station transmission powercontrol system according to claim 5, wherein said mobile station detectsa communication reception quality, and said mobile station sets saidpower increasing symbol in said transmission power control bit in theevent that said communication reception quality does not exceed adesired quality, and sets said power decreasing symbol in saidtransmission power control bit in the event that said communicationreception quality exceeds said desired quality.
 7. A base stationtransmission power control system according to claim 5, wherein saidmobile station intermittently transmits said primary base stationinformation to said soft hand over base station group.
 8. A base stationtransmission power control system according to claim 5, wherein saidbase station controls the transmission power of the transmission signalto the mobile station according to one of said power increasing symboland said power decreasing symbol in the event that said primary basestation information in the transmission power control signals isconsistent with the base station information of said base station.
 9. Abase station transmission power control system according to claim 5,wherein the restricted transmission power is a minimum transmissionpower.
 10. A communication control method in a code division multiaccess cellular mobile radio communication system, said communicationsystem comprising a plurality of base stations respectively announcingunique pilot signals and a mobile station which is capable ofsimultaneously establishing connection with a soft hand over basestation group comprising some of base stations out of said plurality ofbase stations, said communication control method comprises: a step ofdetecting a primary base station among said base stations, a receptionlevel of a pilot signal received from the primary base station which isthe maximum level among reception levels of pilot signals received fromrespective base stations in said soft hand over base station group; astep of setting one of a power increasing symbol and a power decreasingsymbol in a transmission power control bit; and a step of transmittingsaid transmission power control bit and primary base station informationto said soft hand over base station group.
 11. A communication controlmethod according to claim 10, further comprising: a step of detecting acommunication reception quality, a step of receiving a transmissionpower control signal which includes said primary base stationinformation, and a step of restricting a transmission power of atransmission signal to the mobile station in the event that said primarybase station information is not consistent with the base stationinformation of said base station.
 12. A communication control methodaccording to claim 11, wherein the restricted transmission power is aminimum transmission power.
 13. A communication control method accordingto claim 10, wherein said power increasing symbol is set in saidtransmission power control bit in the event that said communicationreception quality does not exceed a desired quality, and said powerdecreasing symbol is set in said transmission power control bit in theevent that said communication reception quality exceeds said desiredquality.
 14. A communication control method according to claim 10,wherein in said primary base station information is intermittentlytransmitted to said soft hand over base station group.
 15. Acommunication control method according to claim 10, further comprising astep of controlling said transmission power of the transmission signalto the mobile station according to one of said power increasing symboland said power decreasing symbol in the event that said primary basestation information in the transmission power control signal isconsistent with the base station information of said base station.
 16. Amobile station in a code division multi access cellular mobile radiocommunication system comprising a plurality of base stationsrespectively announcing unique pilot signals, said mobile station beingcapable of simultaneously establishing connection with a soft hand overbase station group comprising some of base stations out of saidplurality of base stations in the system, said mobile stationcomprising; a primary base station detecting unit which detects primarybase station which transmits a pilot signal of the maximum receptionlevel at said mobile station among received pilot signals from said basestations in said soft hand over base station group; a base stationtransmission power control signal determining unit which sets a basestation transmission power control signal indicating to increase ordecrease a transmission power; and a control signal transmitting unitwhich transmits primary base station information detected by saidprimary base station detecting means and said base station transmissionpower control signal determined by said base station control signaldetermining means to said base station group in soft hand over.
 17. Amobile station in a code divisional multi access cellular mobile radiocommunication system comprising a plurality of base stationsrespectively announcing unique pilot signals, said mobile station beingcapable of simultaneously establishing connection with a soft hand overbase station group comprising some of base stations out of saidplurality of base stations in the system, said mobile stationcomprising: a reception quality detecting unit which detects acommunication reception quality, a primary base station detecting unitwhich detects primary base station which transmits a pilot signal of themaximum reception level at said mobile station among received pilotsignals from said base stations in said soft hand over base stationgroup; a base station transmission power control signal determining unitwhich sets a base station transmission power control signal indicatingto increase or decrease a transmission power; and a control signaltransmitting unit which transmits a primary base station informationdetected by said primary base station detecting unit and said basestation transmission power control signal determined by said basestation control signal determining unit to said base station group insoft hand over; wherein said control signal transmitting unit transmitssaid base station transmission power control signal determined by saidbase station control signal determining unit to the base station groupin soft hand over or intermittently transmits the primary base stationinformation detected by said primary base station detecting unit andsaid base station transmission power control signal determined by saidbase station control signal determining unit to said base station groupin soft hand over.
 18. A communication control method in a code divisionmulti access cellular mobile radio communication system, saidcommunication system comprising a plurality of base stationsrespectively announcing unique pilot signals, said mobile station beingcapable of simultaneously establishing connection with a soft hand overbase station group comprising some of base stations out of saidplurality of base stations in the system, said control method comprisingthe steps of: detecting a primary base station which transmits a pilotsignal of the maximum reception level at said mobile station amongreceived pilot signals from said base stations in said soft hand overbase station group; setting a base station transmission power controlsignal indicating to increase or decrease a transmission power; andtransmitting primary base station information corresponding to saiddetected primary base station and said base station transmission powercontrol signal to the soft hand over base station group.
 19. Acommunication control method to claim 18, further comprising the stepof: detecting a communication reception quality, wherein said basestation transmission power control signal is set for increasing thetransmission power in the event that the detected communicationreception quality does not exceed a desired quality and said basestation transmission power control signal is set for decreasing thetransmission power in the event that detected communication receptionquality exceeds the desired quality.
 20. A communication control methodto claim 18, wherein said base station transmission power control signalis continuously transmitted to said base stations in said soft hand overbase station group or the primary base station information detected isintermittently transmitted to said base stations in said soft hand overbase station group.